This invention relates to the preparation of polymeric chromium complexes. More particularly, it relates to the preparation of such complexes polymerized through carbon-to-carbon bonds rather than through olation.
Methacrylato chromic chloride and other related Werner complexes are well known for use as coupling agents between various polymers and other materials such as metals, oxides and glass. U.S. Pat. No. 2,544,666 -- Goebel and Iler, one of many relating to such compositions, describes processes useful in making such complexes and is incorporated herein by reference. Dimers, trimers and polymers of such compositions are known to form through olation or oxolation by means of two or more chromium atoms being joined by oxygen bridges formed by hydroxyl groups or by oxygen atoms alone. Such olation or oxolation normally occurs after the complex has been adsorbed on the surface of a material. The chromium group is typically bonded to the substrate surface through an oxygen atom, and the various chromium groups can be bonded to each other through olation or oxolation, thereby forming a thin or monomolecular layer of complex on the surface. The opposite end of the complex, which may be a short or long chain carboxylic acid, gives desired characteristics to the surface such as hydrophilic or hydrophobic behavior or additional reactivity.
Although it is known to link such complex molecules on surfaces through olation or oxolation, similar materials are not generally available in which the carboxylic acid end of the complex molecule is a polymer to obtain characteristics of the polymers that can be formed.
It is known that organic polymers containing complexed chromium atoms can be prepared by reacting a basic chromium salt with an organic polymer containing carboxylic acid groups in a suitable solvent, as described in British Patent 862,490. However, working with preformed organic polymers, particularly those of high molecular weight, can be difficult, awkward or time consuming when dissolution is slow and solution viscosities are high. This can hinder the formation of the desired polymeric chromium complexes.